Control devices in a motor vehicle are increasingly supplied with voltage on a continuous basis (also referred to as clamp 30 capability) in order to be able to execute certain monitoring and control functions even when the ignition is shut off. This may involve an access and entry authorization or a diagnosis case, for example. To reduce energy consumption, the control devices are brought into a so-called sleep mode. This is done either by switching off the voltage regulator or by entering a corresponding operating mode of the micro-controller.
When required, the control device must be awakened. This is accomplished either via a line to a wake-up input of the user's micro-controller provided for this purpose, or to a wake-up input of the voltage regulator. In the systems used today, which are generally networked, this may also occur by activity on the bus lines.
This has the disadvantage that either a separate wake-up line must be provided to all required control devices, or, in the case of a wake-up via the bus, all control devices, even those not required, are reactivated by intended or unintended bus activity, either by communication on the bus or by interference on the bus.
It is an object of the present invention to selectively wake up only those control devices that are needed to carry out the required functions, using the bus utilized in motor vehicles, in particular a CAN bus.